1. Field of the Invention
The present invention relates to a driver for driving the display panel and a method for reading/writing in memory thereof and thin film transistor liquid crystal display (TFT-LCD) using the same, in particular, to a driver for driving the display panel and a method for deferring to read/write in memory thereof and thin film transistor liquid crystal display (TFT-LCD) using the same.
2. Description of Related Art
The rapid development of multimedia has most probably benefited from the great advancement of semiconductor module or display apparatus. As to display, the TFT-LCD with high definition, preferred space utilization, low power consumption, and no radiation has gradually become the mainstream of the market.
Generally speaking, in a conventional driving structure of the TFT LCD, the AC mode common voltage driving structure (for example, the line inversion display technology) is usually applied to middle size or small size TFT-LCD (that is to say, apply the AC common voltage to the common electrode), and the DC mode common voltage driving structure (for example, the dot inversion display technology) is usually applied to big size TFT-LCD (that is to say, apply the DC common voltage to the common electrode).
The video signal transmitting method of the display panel in the conventional TFT-LCD is the sequence transmitting method, namely, all the scan lines in the display panel are driven for turning on respectively by the scan signal outputted from the gate driver so as to receive the video input data signal provided by the driver. This kind of transmitting method is so-called non-interlaced scanning.
However, if said non-interlaced scanning video transmitting method and the line inversion display technology are used at the same time, the whole power consumption will be increased because the AC common voltage applied to the common electrode will be inverted on each scan line.
In order to reduce the whole power consumption of the TFT-LCD, it's an existing way that using non-sequence transmitting method as the video transmitting method of the display panel in the TFT-LCD instead of sequence transmitting method. This kind of transmitting method is so-called interlaced scanning. Thereby if the interlaced scanning video transmitting method and the line inversion display technology are used at the same time, the AC common voltage applied to the common electrode will only be inverted on each frame, so it can be understand that the whole power consumption of the TFT-LCD will be significantly reduced.
Although said method for reducing the whole power consumption of the TFT-LCD can gain the corresponding effect, the new concomitant question is a tearing effect which occurs at the time of the video animation frame is being displayed on the TFT-LCD. The tearing effect can be simply described that a part of (almost 50%) video input data of the prior video frame will be remained when the recent video frame is being displayed on the TFT-LCD, so as to the TFT-LCD displays an improper video frame.
The reason of the occurring of tearing effect which happened when interlaced scanning mode is used in the video transmitting method is that: in general, said driver include an memory which carry out an improper read mode when interlaced scanning is adopted, so the wrong data will be inputted into display panel and the TFT-LCD will display a wrong video frame to user watched.
It will be described as below that the method of reading/writing in conventional memory within driver when the non-interlaced scanning mode is used in the video transmitting method of the display panel in the TFT-LCD.
Firstly, FIG. 1 is a diagrammatic drawing showing the non-interlaced scanning mode of the display panel 101 in the conventional TFT-LCD 100. Referring to FIG. 1, it is clearly disclosed that the display panel 101 includes 320 scan lines SL. The display panel 101 is driven by gate driver 103 with a non-sequential mode to turn on the scan lines SL and corresponding to receive the video input data provided by the driver 105.
In brief, the gate driver 103 will firstly turn on all of the odd scan lines SL (1, 3, 5, . . . , 319) of the display panel 101 sequentially and then turn on all of the even scan lines SL (2, 4, 6, . . . , 320) of the display panel 101 sequentially. This kind of driving method will separate one frame period in the display panel 101 into odd field and even field. The odd field and even field can be combined together to form a so-called “frame”.
FIG. 2 shows a read mode of the conventional memory 201 within the driver 105 for the first frame period when the display panel 101 adopts the interlaced scanning mode as video transmitting method. Referring to FIG. 1 and FIG. 2, when the interlaced scanning mode is adopted, the read mode of the memory 201 (for example, a SRAM) within the driver 105 is: firstly, writing sequentially video input data into the memory 201 from the first video input data D_in_1_1 to the 160th video input data D_in_1_160, and at the same time, reading the video input data for odd field from memory 201 and transmitting it to the display panel 101.
It is clearly disclosed in FIG. 2 that when the fist video input data D_in_1_1 of the first frame is written into the memory 201 within the driver 105, the video input data D_out_1_1 is correctly outputted as the first video input data of the odd field. However, when the second video input data D_in_1_2 of the first frame is written into the memory 201 within the driver 105, an improper video input data is mistakenly outputted as the third video input data D_out_1_3 of the odd field because the third video input data D_out_1_3 hasn't been written into the memory 201 within the driver 105 heretofore.
It can be understood that unknown video input data are outputted from the third video input data D_out_1_3 to the 319th video input data D_out_1_319 of the odd field. However, from the second video input data D_out_1_2 to the 320th video input data D_out_1_320 of the even field, all the video input data of the even field will be correctly outputted because the data has been already written into the memory 201 within the driver 105 heretofore.
FIG. 3 shows the read mode of the conventional memory 201 within the driver 105 for the second frame period when the display panel 101 adopts the interlaced scanning mode as video transmitting method. Referring to FIG. 1˜FIG. 3, after the reading/writing for the first frame is accomplished, the writing for the second frame will start from the first video input data D_in_2_1 to the 160th video input data D_in_2_160 of the second frame, and the same time the video input data of the odd field will be read and outputted to the display panel 101.
It is clearly disclosed in FIG. 3 that when the fist video input data D_in_2_1 of the second frame is written into the memory 201 within the driver 105, the video input data D_out_2_1 is correctly outputted as the first video input data of the odd field. However, when the second video input data D_in_2_2 of the second frame is written into the memory 201 within the driver 105, the video input data D_out_1_3 which belongs to the first frame period is mistakenly outputted as the third video input data D_out_2_3 of the odd field.
It can be understood that improper video input data D_out_1_3˜D_out_1_319 which belongs to the first frame are mistakenly outputted as the third video input data D_out_2_3 to the 319th video input data D_out_2_319 of the odd field. However, from the second video input data D_out_2_2 to the 320th video input data D_out_2_320 of the even field, all the video input data of the even field will be correctly outputted because the data has been already written into the memory 201 within the driver 105 heretofore.
In other words, it can be understood that when the video input data D_out_2_3˜D_out_2_319 of odd field need to be read, actually, the video input data D_in_1_3˜D_in_1_319 of the odd field which belongs to the first frame is read. Similarly, a part of (almost 50%) video input data of the prior video frame will be remained in the third frame, the fourth frame and so on, and it's the causation for said tearing effect.
In order to solve the tearing effect of the TFT-LCD, some people consider that it is feasible to add one more memory to the driver. For the driver has two memories, one memory process the reading operation, and the other memory process the writing operation. The two memories can read or write video input data alternately. This idea can resolve the tearing effect of the TFT-LCD. However, it is hard to set two memories in the driver because the two memories will occupy overfull area of the driver. In general, one memory will occupy 60% area of the driver, so it is unsatisfactory to set two memories in one driver. For this reason, said idea is only an assumption but cannot be applied in the conventional driver.